Originally Posted by sinoflyer

This is an absolutely irresponsible advise. Have you done this yourself? OP can certainly receive TWOV with the PEK-SIN ticket, but how do you suppose OP would be able to check into the return PEK-DTW flight when their TWOV is designated for continuation to SIN? Are you suggesting that OP should toy with Chinese bureaucracy can like you can in liberal democracies? "I change my mind" is not going to sway one single official in the interrogation room. Be prepared to use that PEK-SIN ticket, and be prepared to buy a oneway SIN-YYZ ticket to get back home.